JP6244602B2 - Clamp device for wax mold injection molding and method for producing wax mold - Google Patents

Description

  The present invention relates to a clamping device for wax mold injection molding and a method for manufacturing a wax mold, and in particular, a clamping device used for fixing a rubber mold in wax mold injection molding in lost wax precision casting and a wax using the clamping device. The present invention relates to a mold manufacturing method.

  Decorations, accessories, jewelry, etc., mainly using precious metals, are small, complex, and more precise. There is a desire to produce such products in large quantities, and lost wax precision casting has been developed in the industry. Of course, the present invention can also be applied to manufacturing precision industrial parts other than those described above.

Lost wax precision casting in the jewelry manufacturing industry has the following processes.
The first process is the process of making the prototype.
The second process is a process of manufacturing a rubber mold having a cavity having the same shape as the original mold.
The third step is a step of injecting the wax dissolved in the rubber mold and taking it out to produce a wax mold having the same shape as the original mold. In general, many wax molds are produced by repeating the third step.
In the fourth step, a large number of wax molds manufactured in the third step are attached in a tree shape while dissolving the end of the wax mold around the wax rod, and this is installed in a cylindrical heat-resistant container, and gypsum is poured. The process of creating a plaster mold.
The fifth step is to use an electric furnace or gas furnace, etc., to dissolve away the wax inside the gypsum mold at a low temperature, completely burn the wax adhering to the inside of the cavity at a medium temperature, and further raise the temperature to increase the temperature. A firing process in which after the steel has developed a strength that can withstand the impact of pouring a noble metal, it is lowered to a temperature suitable for pouring the noble metal.
The sixth process is a casting process in which precious metal is poured into a gypsum mold that has many of the same cavities as the original mold.
The seventh step is to quickly cool the gypsum mold with water when the precious metal has hardened. Process.

  The rubber mold manufacturing method in the second step will be described with reference to FIG. In the second step, a mold frame (not shown) having a size corresponding to the size of the rubber mold 3 to be created, a prototype 1 and parts 2 (runner 2a and gate 2b) are used. The bottom of the formwork is closed with a plate, and the material before vulcanization of silicon rubber is placed in the lower half, and then the part 1 is bonded to the original mold 1 and then the material before vulcanization is placed in the upper half. Put the upper part of the frame with a plate, and vulcanize by pressing to raise the temperature. A two-component solidified silicone rubber may be used instead of the vulcanizable rubber.

  When the silicon rubber has hardened and has the inherent elasticity of the rubber, take out the rubber mold 3 from the frame, insert the zigzag cut 3c, take out the original mold 1 and the part 2 adhered to it, and raise the rubber mold. The rubber mold 3a and the lower rubber mold 3b are separated. Thereby, the rubber mold 3 having the cavity 4 having the same shape as the original mold 1 and the component 2 is obtained. By inserting such a cut 3c into the entire separation surface, when the upper and lower rubber molds 3a and 3b are combined, it is possible to accurately match them and to accurately reproduce the internal cavity shape.

  Such a notch 3c also has an effect of facilitating vacuuming and sealing of the pressurized wax when a wax mold is produced by injecting wax into the rubber mold 3. When taking out the wax mold from the rubber mold 3, after separating the upper rubber mold 3a from the mating surface (cut) 3c and then taking out the work while deforming the lower rubber mold 3b, even if the wax mold has a complicated shape, It can be easily removed without breaking. In some cases, the inside of the rubber mold may be divided into several parts or cores may be inserted.

  Since the original mold has various sizes, the size and thickness of the rubber mold change in accordance with the size. Also, the hardness of the rubber is often changed in accordance with the durability of the rubber mold and the difficulty level when the wax mold is taken out from the rubber mold.

  2 and 3 are conceptual diagrams of a wax type injection molding machine and a clamp device used in the third step.

  The wax type injection molding machine 6 has an injection nozzle 7 and basically has a function of evacuating the cavity 4 in the rubber mold from the injection nozzle 7 and a function of pressurizing and injecting the dissolved wax. Furthermore, in order to produce high-quality wax molds in large quantities with high yield, functions such as melt wax temperature control, injection nozzle temperature control, injection pressure control, evacuation time control, and injection time control may be required. is there.

  The clamping device 5 sandwiches the rubber mold 3 between a mounting plate 9 and a clamp plate 10 driven by a clamping force generator 11 to apply a clamping force (clamping force F1, clamping reaction force F2), thereby causing an injection nozzle 7 and a gate 4a. The rubber mold 3 is pressed against the injection nozzle 7 with a pressing force F3 and sealed. In this state, wax is injected from the injection nozzle 7 into the cavity 4 of the rubber mold 3.

  The volume and shape of the original mold 1 are various, and therefore the length when viewed from above the rubber mold 3, 3 'manufactured from the original mold and the thickness when viewed from the side are also varied. Accordingly, in order to appropriately inject the melted wax into the cavity 4 in the rubber mold and to manufacture a predetermined wax mold, a function required in addition to the basic functions shown in FIG. Will occur.

  The thickness of the rubber mold 3 is not always constant, and the clamp plate 10 and the mounting table 9 are not completely parallel. Therefore, the clamp force generator 11 and the clamp plate 10 swing the clamp plate 10 by a spherical bearing. It is common to couple by a floating mechanism 12 that supports it.

  In order to clamp and properly seal the rubber mold 3, it is necessary to apply a uniform surface pressure to the rubber mold mating surface 3c. Therefore, it is desirable to clamp the entire surface of the rubber mold by applying an average force. Since the rubber molds 3 and 3 'have various sizes, it is necessary to move the point of application of the clamping force F1 (clamping force generator 11) within a certain range R1.

  The vertical movement mechanism 5b is for adjusting the height of the mounting table 9 within a certain range R2 so that the gates 4a of the rubber dies 3, 3 ′ having different thicknesses can be adjusted to the height of the injection nozzle 7. Is.

  The front-rear moving mechanism 5c is for moving the mounting table 9 in the front-rear direction. By moving the gate 4a of the rubber molds 3 and 3 'in the direction of the injection nozzle 7 by the back-and-forth movement mechanism 5c and generating a pressing force F3, evacuation of the cavity 4 inside the rubber mold 3 in the third step and to the inside Sealing of the pressure when injecting the wax can be performed.

  Further, in order to change the injection pressure of the wax from the injection nozzle 7 in accordance with the shape of the cavity 4 and the properties of the wax, and / or so as not to lose the injection pressure of the wax, the clamping force F1 and the pressing force F3 are set. It needs to be adjusted. However, if the clamping force F1 or the pressing force F3 is excessive, the rubber mold 3 is deformed, and it becomes impossible to take a wax mold close to the original mold.

International Publication No. 2013/038448 JP 2002-254137 A

  FIG. 4 shows the force balance when the rubber mold 3 is clamped by the clamp device 5 and the wax is injected.

  The clamp force generator 11 is a device for applying a clamp force F <b> 1 to the clamp plate 10.

  When the rubber mold 3 mounted on the mounting table 9 is clamped between the mounting table 9 and the clamp plate 10, the rubber mold 3 is deflected (compressed) D1 by the clamping force F1, and the volume and shape of the cavity 4 are also changed. (4 → 4 ′). At this time, if the elastic coefficient of the rubber mold 3 is K, an elastic force Fr of Fr = K × D1 is generated in the rubber mold 3. F1 and Fr are equal in magnitude and opposite in direction, and force balance. The clamping force F1 does not act on the cross-sectional area S of the cavity 4 ', but acts on the area A of the rubber mold mating surface 3c. Therefore, the value of F1 / A = K × D1 / A means the surface pressure acting on the rubber mold mating surface 3c of the rubber mold 3. As shown in FIG. 1, in the general rubber mold 3, the area S is smaller than the area A, and when calculating the surface pressure, the total cross-sectional area of the rubber mold 3 is A + S≈A. Often it can be calculated.

  The rubber mold 3 is advanced and pressed against the injection nozzle 7, and after evacuation, the wax is injected from the nozzle 7 at a certain pressure P to fill the inside of the rubber mold 3 with the wax. At this time, a force Fp obtained by multiplying the cross-sectional area S and the injection pressure P is generated in the cavity 4, and the resultant force of the clamping force F1 and Fr + Fp balances. Therefore, the elastic force Fr of the rubber mold 3 is changed from F1 to F1-Fp. The surface pressure of the rubber mold mating surface 3c decreases to (F1-Fp) / A. Along with this, the deflection of the rubber mold 3 decreases from D1 to D2 (D2 <D1), and the volume and shape of the cavity 4 change (4 ′ → 4 ″).

  The decrease in the elastic force Fr causes the wax to ooze out from the rubber mold mating surface 3c at the time of wax injection, and causes the need for deburring and the like in a subsequent process. In order to prevent this, if the clamping force F1 is excessively increased, the burden on the rubber mold 3 is increased, and the volume and shape (4 ″) of the cavity at the time of wax injection are changed from the initial volume and shape (4). It will change greatly. The deformation of the cavity is a problem because it means that the product shape is different from that of the prototype 1. Clearly, this problem is significant when the product is an industrial precision part. The change in the cavity volume causes the metal usage of the product to become unstable. In particular, when the product is a precious metal, even a slight increase in the amount of use produces a large amount of the product, which greatly affects the profit management of the manufacturer.

  Therefore, an appropriate clamping force F1 must be determined according to the type of rubber mold 3 and the injection pressure P. However, the rubber mold 3 has various sizes and hardnesses, and the injection pressure P needs to be changed according to the type of wax, the size and shape of the cavity 4, etc., and is appropriate based on such various factors. It is practically impossible to obtain the correct clamping force F1. For this reason, the clamping force F1 is determined for each rubber mold 3 by trial and error.

  The manufacturer performs such trial and error for each of the large number of rubber dies 3, and further inputs manufacturing conditions such as injection pressure P and clamping force F1 determined thereby to the apparatus for each rubber dies 3 to be stored. Work (Patent Document 2) is forced. In addition, because of trial and error, operator skill is required to determine the optimum manufacturing conditions, increasing the difficulty of manufacturing high-quality products. Since it was determined by trial and error, there were variations in manufacturing conditions, which caused variations in product volume and shape.

  The present invention discloses the following invention.

<Viewpoint 1>
A mounting table for mounting the rubber mold;
A clamp plate movable in the vertical direction;
A clamping force generator for applying a clamping force to the clamping plate;
A clamping device for wax mold injection molding that clamps the rubber mold between the mounting table and the clamp plate,
A surface pressure measuring mechanism for measuring the surface pressure generated in the rubber mold;
An input means for inputting the surface pressure target value;
The clamp apparatus further comprising a control means for controlling the clamping force based on the surface pressure target value and the surface pressure measured by the surface pressure measuring mechanism.

<Viewpoint 2>
2. The clamp device according to aspect 1, further comprising a lock mechanism for fixing a vertical position of the clamp plate with respect to the mounting table.

<Viewpoint 3>
3. The clamp device according to aspect 1 or 2, wherein a pressure receiving plate having a lower hardness than the rubber mold is attached to the lower surface of the clamp plate.

<Viewpoint 4>
The surface pressure measuring mechanism has a surface pressure sensor,
The clamp device according to any one of aspects 1 to 3, wherein the surface pressure sensor is attached to a recess formed on a lower surface of the clamp plate.

<Viewpoint 5>
The injection of the wax into the rubber mold is performed in a state where the clamp device is adjacent to the wax mold injection molding machine,
The wax injection direction is a first direction, and a direction in a horizontal plane perpendicular to the first direction is a second direction.
In the surface pressure sensor, the distance in the first direction from the end of the clamp plate on the wax-type injection molding machine side is 0 to 20 mm, and the surface pressure sensor from the point of application of the clamping force on the clamp plate The clamp device according to aspect 4, wherein the clamp device is installed in a region in which the distance in the second direction is 5 mm to 17.5 mm.

<Viewpoint 6>
6. The clamping device according to aspect 4 or 5, wherein a plurality of the surface pressure sensors are installed at spaced positions in the first direction and / or the second direction.

<Viewpoint 7>
A wax mold manufacturing method using the clamp device according to any one of aspects 1 to 6,
A first step of clamping the rubber mold according to the control of the control means;
A second step of maintaining the clamping force at the end of the first step;
A method of manufacturing a wax mold, comprising: a third step of injecting wax into the rubber mold after a predetermined time has elapsed since the end of the first step.

The problem to be solved by the present invention has not been solved to date even though it has been desired in the industry for over 20 years. The circumstances of (1) to (3) below are the problems that the above-mentioned invention is trying to solve for a long time, and have been attempted to be solved. This is proof that the inventions 1 and 7 could not be conceived.
(1) Patent Document 2 is the only conventional technique for tackling the problem to be solved by the above invention.
(2) Compared with the inventions according to viewpoints 1 and 7, the apparatus of Patent Document 2 has problems in terms of human costs related to data input and the like, management costs, efficiency, and convenience.
(3) The product of Patent Document 2 having the problem (2) described above has achieved commercial success for a period of about 10 years from its release to today, despite the high price of the device. I am paying.

  Considering the above, it can be said that the inventions of viewpoints 1 and 7 are not easily conceived at least in this industry.

  In the present application, up and down, front and rear, and left and right mean directions perpendicular to each other. The first and second directions mean directions perpendicular to each other in the horizontal plane. However, this definition is not strict and should be interpreted flexibly as long as the effects of the invention can be achieved. As long as the effect of the invention can be achieved, the angle between the top, bottom, front, back, left and right can be different from the vertical. Further, the vertical direction does not necessarily mean the vertical direction. For example, in a form in which the clamping device in the following embodiment is used in a horizontal position, the vertical direction may be a direction in a horizontal plane.

FIG. 1 is an explanatory diagram of a rubber mold manufacturing method. FIG. 2 is a side view of the wax-type injection molding machine and the clamping device. FIG. 3 is a side view of the clamping device. 4A to 4C show force balance when a rubber mold is clamped by a clamp device and wax is injected. Fig.5 (a) shows the clamp apparatus 5A which concerns on one Embodiment of this invention. FIG. 5B shows a clamp device 5B according to another embodiment. Fig.6 (a) shows transition of the typical surface pressure measured value Pm in 5 A of clamp apparatuses in a 3rd process. FIG. 6B shows a transition of a typical surface pressure measurement value Pm in the clamp device 5 in the third step. FIG. 7 is a front view of a clamp device 5C according to an embodiment of the present invention. FIG. 8 is a side view of a clamp device 5C according to an embodiment of the present invention. FIG. 9 shows the lock mechanism 20A. FIG. 10 shows the wedge receiving member 25. FIG. 11 illustrates the wedge effect due to having the recess 25c. FIG. 12 shows a modified form of the locking mechanism. FIG. 13 shows a modified form of the locking mechanism. FIG. 14 shows the surface pressure measuring mechanism 30. FIG. 15 shows a preferable range R of the installation positions of the surface pressure sensors 31A and 31B. FIGS. 16A and 16B show the top and side surfaces of exemplary surface pressure sensors 31A to 31D. FIG. 17 shows a mechanism of surface pressure measurement by the surface pressure measurement mechanism 30.

  The principle of the present invention will be described with reference to FIG. 5A showing a clamp device 5A according to an embodiment of the present invention.

  The clamp device 5 </ b> A includes a mounting table 9, a clamp plate 10, a clamp force generator 11, a surface pressure sensor 31, a target value input unit 40, and a control unit 50. In the present embodiment, the surface pressure sensor 31 constitutes a surface pressure measuring unit.

  The clamp force generator 11 presses (clamps) the rubber mold 3 between the mounting table 9 and the clamp plate 10 by lowering the clamp shaft 11a by supplying air S, and the air S exhausts and the action of the return spring 11b. It is preferable to use a single-action air cylinder that raises the clamp shaft 11a. This is because the friction between the piston and the cylinder wall and other friction can be reduced, and the pressing force can be freely changed by controlling the supply pressure of the air S.

  The surface pressure sensor 31 provides the control unit 40 with a signal corresponding to the surface pressure generated in the rubber mold 3 by the clamp. Preferably, the surface pressure sensor 31 is attached to the lower surface of the clamp plate 10. The number of the surface pressure sensors 31 may be one or plural. In the clamp device 5A, the surface pressure sensor 31 is installed at a position corresponding to the rubber mold mating surface 3c (a part other than the cavity 4 and the gate 4a) in the rubber mold 3. The surface pressure sensor 31 generates a signal corresponding to the pressure generated on the rubber mold mating surface 3c. Therefore, the pressure generated on the rubber mold mating surface 3c can be obtained based on the signal from the surface pressure sensor 31.

  The target value input unit 40 is means for inputting the surface pressure target value Pa to the control unit 50. The target value input unit 40 can be configured with, for example, a keyboard, a touch panel, a mouse, a button, or the like.

  The controller 50 controls the clamping force F <b> 1 by the clamping force generator 11 based on the signal from the surface pressure sensor 31. The clamping force F1 can be controlled by controlling the supply of air S to the clamping force generator 11. Preferably, the control unit 50 obtains an appropriate calculation value from the signal of the surface pressure sensor 31, and feedback-controls the supply of the clamping force F1 or the air S based on the calculated value. In a preferred embodiment, the control unit 50 controls the supply of the air S to the clamping force generator 11 based on the surface pressure (surface pressure measurement value Pm) obtained from the signal of the surface pressure sensor 31. Hereinafter, for convenience of explanation, the description will be made on the premise of this aspect. The controller 50 supplies the air S when the measured surface pressure value Pm is less than the set surface pressure Pa, and stops supplying the air S when the measured surface pressure value Pm is equal to or greater than the set surface pressure Pa. . When the surface pressure measurement value Pm is equal to or greater than the surface pressure setting value Pa, the air S may be exhausted. The control of the control unit 50 can be PID control.

The inventor of the present application uses the clamping device of the present invention and is necessary to prevent the exudation of wax with respect to the rubber mold 3 having various sizes / materials and various hollow shapes currently used in the industry. An experiment was conducted to examine the minimum surface pressure (hereinafter referred to as seal pressure Ps) of the rubber mold mating surface 3c. As a result, it is possible to statistically grasp the seal pressure Ps from only the injection pressure P of the wax. Depending on the size / material of the rubber mold 3 and the size / shape of the cavity 4, the seal pressure Ps It was found that the pressure Ps was not greatly affected. In an experiment conducted by the present inventor, an approximate value of the seal pressure Ps is obtained by a linear expression such as the following expression (1) for various rubber molds 3 having different sizes and materials, and the sizes and shapes of the cavities 4. The result was possible. (C1 and C2 are constants.)
Ps = C1 × P + C2 (1)

  Therefore, a value obtained by adding a certain margin (margin for covering a decrease in the measured pressure value Pm at the time of wax injection) to the approximate value of the seal pressure Ps obtained by the above formula (1) or the like is a surface pressure target. By setting the value Pa, it is possible to inject the wax into the rubber mold 3 without causing the wax to ooze out. For example, a value obtained by a simple mathematical expression such as C3 × Ps can be used as the surface pressure target value Pa. C3 is a constant of about 1.1 to 1.5, for example.

  Fig.6 (a) shows transition of the typical surface pressure measured value Pm in 5 A of clamp apparatuses in a 3rd process. The horizontal axis is time. Generally, the rubber mold 3 is arranged so that the point of action of the clamping force F1 is at the center of the rubber mold 3, and the rubber mold 3 is clamped with a uniform surface pressure. When the control unit 50 starts controlling the air S (time t0), the clamp plate 10 comes into contact with the upper surface of the rubber mold 3 at a certain time t1, and thereafter, the deflection (compression) of the rubber mold 3 increases and the surface pressure increases. The measured value Pm increases. When the surface pressure measurement value Pm reaches the surface pressure target value Pa (time point t2), the control unit 50 stops the supply of the air S. Thereby, the surface pressure measurement value Pm is maintained at a constant value (surface pressure target value Pa). Thereafter, when the wax injection is started at time t3, the deflection of the rubber mold 3 is reduced by the injection pressure P of the wax, and the surface pressure measurement value Pm is reduced. However, the surface pressure target value Pa is appropriately set as described above. In this case, the surface pressure measurement value Pm can be prevented from being lower than the seal pressure Ps. Therefore, it is possible to inject the wax into the rubber mold 3 without causing the wax to ooze out with respect to various rubber molds 3 having different sizes / materials and the sizes / shapes of the cavities 4. Further, complicated operations such as determination of the clamping force F1 and the like by conventional trial and error and input to the apparatus are unnecessary or reduced, and a product with high quality can be manufactured more easily. Furthermore, by setting an appropriate surface pressure target value Pa, it is possible to prevent excessive clamping force F1 from being applied to the rubber mold 3, and to reduce the load on the rubber mold 3 and the change in the volume / shape of the cavity 4. Become.

  Normally, this state is maintained for a certain time (until a certain time t5) from the time t4 when the injection of the wax is completed until the wax cools / solidifies to some extent. Thereafter, the rubber mold 3 is removed from the injection nozzle 7 to complete the third step.

  The control of the air S by the control unit 50 may be performed only between the time t0 and the time t3, but the control may be continued for a predetermined time after the time t3. When the control is continued after the time point t3, the controller 50 supplies the air S when the surface pressure measurement value Pm decreases after the time point t3, so that the reduction range of the surface pressure measurement value Pm becomes small. Therefore, a smaller surface pressure target value Pa can be set.

  FIG. 5B shows a clamp device 5B according to another embodiment. The clamp device 5B has the same configuration as that of the clamp device 5A except that the clamp device 20 is provided. The lock mechanism 20 is disclosed in PCT / JP2015 / 073015 previously filed by the applicant of the present application, and is used to fix the vertical position of the clamp plate 10 with respect to the mounting table 9 in a state where the rubber mold 3 is clamped. Mechanism. By fixing the position of the clamp plate 10, it is possible to reduce the reduction width of the surface pressure measurement value Pm at the time of wax injection. As a result, the surface pressure target value Pa can be made smaller (a value closer to the seal pressure Ps), and the load on the rubber mold 3 and the volume and shape of the cavity due to excessive clamping force F1 can be further reduced. It becomes possible to make it smaller. As a result, it is possible to manufacture the product more faithfully with the prototype 1, and to improve the quality of precision parts and the like.

  FIG.6 (b) shows transition of the typical surface pressure measurement value Pm in the clamp apparatus 5B in a 3rd process. The horizontal axis is time. Similarly to the case of FIG. 6A, at the time t2 when the surface pressure measurement value Pm reaches the surface pressure target value Pa (or an appropriate timing from the time t2 to the time t3 at which the wax injection starts). The position of the clamp plate 10 is fixed by the lock mechanism 20. Thereby, the decrease width of the surface pressure measurement value Pm by the wax injection after the time point t3 becomes smaller than that in the case of FIG. 6A (ideally, the decrease width becomes zero). Therefore, the margin of the surface pressure target value Pa with respect to the seal pressure Ps can be further reduced, and the load on the rubber mold 3 and the change in the volume and shape of the cavity due to the clamping force F1 can be further reduced. The position of the clamp plate 10 by the lock mechanism 20 may be fixed manually or under the control of the control unit 50. The control unit 50 preferably controls the lock mechanism 20 to fix the position of the clamp plate 10 at the timing of the time point t2 (or an appropriate timing between the time point t2 and the time point t3).

  7 to 9 show a particularly preferred form of the clamping device 5C. 7 and 8 correspond to the portion above the rubber mounting table 9 of the clamp mechanism 5a in FIG.

  The clamp device 5C of the present embodiment includes a clamp mechanism unit housing 8, a mounting table 9 having a substantially horizontal mounting surface for mounting the rubber mold 3, and a clamp plate 10 movable in the vertical direction. A clamping force generator 11, a floating mechanism 12, a clamping force generator moving mechanism 13, a left / right moving mechanism 14, a locking mechanism 20A, and a surface pressure measuring mechanism 30.

  The housing 8 can be formed of a metal material such as a sheet metal. The mounting table 9 has a rubber-type positioning insertion plate 9a formed of an acrylic plate or the like on which the rubber mold 3 can be mounted, and the above-described mounting surface is formed on the rubber-type positioning insertion plate 9a.

  The clamp plate 10 is formed of a substantially flat metal plate or the like. In the clamp plate 10, one or a plurality of recesses 10 b (FIG. 17) for accommodating a below-described surface pressure sensor 31 and one or a plurality of wirings for passing the wiring from the surface pressure sensor 31 to the circuit board 33. A hole 10c (FIG. 14) is formed.

  The clamp force generator 11 is a device for changing the vertical position of the clamp plate 10 with respect to the mounting table 9 and causing the clamp force F1 to act on the clamp plate 10. Preferably, the clamp force generator 11 is a single-acting air cylinder capable of moving the clamp plate 10 up and down by a clamp shaft 11a operated by compressed air and applying a clamp force F1 to the clamp plate 10. is there.

  The clamp shaft 11 a and the clamp plate 10 are connected via a floating mechanism 12. The floating mechanism 12 includes a rocking bearing portion 12a and a movement limiting mechanism 12b.

  The oscillating bearing 12a is coupled to the clamp shaft 11a by a ball joint or the like so that the clamp plate 10 can swing back and forth and right and left.

  The movement limiting mechanism 12b allows the clamp shaft 11a to move in the front-rear direction when the clamp plate 10 is at the top dead center, while the clamp plate 10 of the clamp shaft 11a moves when the clamp plate 10 is lowered from the top dead center. The position in the front-rear direction with respect to is fixed. As a result, when the clamp plate 10 is at the top dead center, the operating point of the clamping force F1 on the clamp plate 10 can be adjusted in the front-rear direction according to the size of the rubber mold 3. In the descending process, the point of action of the clamping force F1 is prevented from shifting.

  The clamp plate 10 has protrusions 10a on the left and right sides, and the clamp mechanism section housing 8 has an engagement portion 8a that engages with the protrusion 10a of the clamp plate 10 at the top dead center. Engaging the protrusion 10a and the engaging portion 8a prevents the clamp plate 10 from moving back and forth together when the clamp shaft 11a moves in the front-rear direction.

  The clamping force generator moving mechanism 13 is a mechanism for moving the clamping force generator 11 in the front-rear direction.

  The clamp force generator moving mechanism 13 rotates the guide shaft 13a for guiding the clamp force generator 11 back and forth, a rack 13b and a pinion 13c for driving the clamp force generator 11 back and forth, and the pinion 13c. The knob 13d is provided.

  The guide shaft 13a is attached to the clamp mechanism section housing 8 with a slight gap, and even if the clamp force generator 11 is operated, a large reaction force does not act on the guide shaft 13a, and the clamp mechanism section housing. Clamp reaction force receivers 13e for directly acting on the body 8 are attached to the left and right in the entire moving direction of the clamp force generator moving mechanism 13.

  When the clamp force generator 11 is moved by the rotation of the knob 13d, a slight gap is provided between the clamp reaction force receiver 13e and the clamp mechanism housing 8, and the clamp shaft can be freely moved. When 11a descends and the rubber mold 3 is clamped, the guide shaft 13a is lifted by the reaction force, and the clamp reaction force receiver 13e comes into close contact with the clamp mechanism housing 8 to receive a large reaction force.

  The vertical position of the clamping force generator moving mechanism 13 with respect to the mounting table 9 is basically fixed. In a state in which the clamp plate 10 clamps the rubber mold 3, the clamp reaction force receiver 13e is in close contact with the clamp mechanism unit housing 8, and the vertical position of the clamp force generator moving mechanism 13 with respect to the mounting table 9 is substantially Fixed.

  The left-right moving mechanism 14 is a mechanism that guides the clamp mechanism portion 5a in the left-right direction according to the force in the left-right direction that acts on the clamp mechanism portion 5a.

  FIG. 9 shows the lock mechanism 20A. As illustrated, the lock mechanism 20 </ b> A includes a lock rod 21, a block member 22, an elastic member 23, an air cylinder 24, and a wedge receiving member 25.

  The lock rod 21 is a flat bar member having a circular hole 21a at one end and a circular hole 21b at the other end. The circular hole 21a is rotatably supported in a horizontal plane around a fixed shaft 13g fixed to the housing 13f of the clamp force generator moving mechanism 13. The circular hole 21b is rotatably supported around a drive shaft 24b formed at the tip of the piston 24a of the air cylinder 24.

  The lock rod 21 has an engaging portion 21c that can be engaged with the clamp shaft 11a at an intermediate position between the circular holes 21a and 21b. The engaging portion 21c can have a complementary shape to the clamp shaft 11a. The engaging portion 21c is provided at a position where the distance N between the circular holes 21a and 21b is sufficiently larger than the distance n between the circular hole 21a and the engaging portion 21c.

  The block member 22 is fixed to the housing 13 f of the clamp force generator moving mechanism 13. An elastic member 23 such as a spring is inserted between the other end side of the lock rod 21 and the block member 22.

  The air cylinder 24 drives the piston 24a in the horizontal direction (left and right in FIG. 8A) by the pressure of the air S1 and the urging force of the elastic member 23. The air cylinder 24 is positioned so that a slight gap is formed between the engaging portion 21c and the clamp shaft 11a when the air S1 is not supplied.

  FIG. 10 shows the wedge receiving member 25. Fig.10 (a) is a perspective view, FIG.10 (b) is CC cross section of FIG.9 (b). The wedge receiving member 25 is a member having a substantially cylindrical outer shape having a protruding portion 25a. The wedge receiving member 25 is formed with a guide hole 25b having substantially the same diameter as that of the clamp shaft 11a for guiding the clamp shaft 11a, and a concave portion 25c opened in the guide hole 25b. The guide hole 25b and the recessed part 25c penetrate the wedge receiving member 25 in the vertical direction. In a preferred embodiment, the recess 25c has an arcuate cross-sectional shape having a smaller diameter than the guide hole 25b formed at the eccentric position of the guide hole 25b. The connecting portion between the guide hole 25b and the recess 25c constitutes friction portions 25d and 25e that generate friction between the clamp shaft 11a. The distance r1 between the friction portions 25d and 25e is smaller than the diameter r2 of the guide hole 25b (clamp shaft 11a).

  On the side surface of the wedge receiving member 25, a notch 25f having a width substantially the same as the thickness of the lock rod 21 for guiding the lock rod 21 in a horizontal plane is formed. For example, the wedge receiving member 25 is preferably an integral member formed by processing a cylindrical rod from the viewpoint of cost and strength. The recess 25c can be processed by an end mill or the like, and the cut portion 25f can be processed by a mill or the like. The wedge receiving member 25 is fixed to the housing 13f in a state where the protruding portion 25a is inserted into the engagement hole 13h of the housing 13f. In the figure, 25g is a receiving hole for the fixed shaft 13g.

The operation of the lock mechanism 20A will be described.
When air S1 is not supplied to the air cylinder 24, there are gaps between the engaging portion 21c and the clamp shaft 11a, and between the clamp shaft 11a and the friction portions 25d and 25e, and the clamp shaft 11a moves freely in the vertical direction. Is possible.

  When air S1 is supplied to the air cylinder 24, the piston 24a rotates the lock rod 21 around the fixed shaft 13g, and the clamp shaft 11a is pressed against the concave portion 25c by the engaging portion 21c. This pressing force causes friction between the clamp shaft 11a and the friction portions 25d and 25e, and the vertical position of the clamp shaft 11a with respect to the mounting table 9 is fixed.

  At this time, since the distance N is sufficiently larger than the distance n, the pressing force from the clamp shaft 11a to the wedge receiving member 25 can be increased. Further, when the pressing force of the clamp shaft 11a acts on two points (friction portions 25d and 25e), a large reaction force is generated by the wedge effect, and the position of the clamp shaft 11a in the vertical direction can be firmly fixed.

  FIG. 11 illustrates the wedge effect due to having the recess 25c. When there is no recess 25c, a drag is generated only at one location of the wedge receiving member 25, and the magnitude of the drag is equal to the pressing force F of the clamp shaft 11a. However, in the present embodiment, the presence of the concave portion 25c generates drag Fa and Fb at the two friction portions 25d and 25e. When the distance r1 between the friction portions 25d and 25e is increased (where r1 <r2), the drag Fa and Fb can be increased as Fa2 and Fb2.

  Since the frictional force acting on the clamp shaft 11a acts as a product of the drag forces Fa and Fb and the friction coefficient, the wedge force can effectively increase the frictional force. Since the coefficient of friction is determined by the material and surface roughness of the outer wall of the clamp shaft 11a and the inner wall of the recess 25c, a spiral groove is formed in the clamp shaft 11a and / or the recess 25c by selecting an appropriate material and finishing an appropriate surface roughness. Etc., it is possible to increase the friction coefficient.

  While the piston 24a moves linearly, the lock rod 21 rotates. However, if the diameter of the circular hole 21b is made slightly larger than that of the drive shaft 24b, there is no problem in the above operation. When the clamp shaft 11a is pressed toward the recess 25c, a force perpendicular to the drive direction of the clamp shaft 11a acts, but if the diameter difference between the clamp shaft 11a and the guide hole 25b is sufficiently small, a clamping force is generated. The function and operation of the device 11 are not adversely affected.

  In this embodiment, the wedge receiving member 25 having the projection 25a, the guide hole 25b, the notch 25f, and the like is shown as a particularly preferable aspect. However, the clamp shaft 11a due to the wedge effect described above has only the friction portions 25d and 25e. Can be fixed, and other configurations can be omitted.

  Various modifications are conceivable for the lock mechanism 20A in the above embodiment.

  FIG. 12 shows a first variation of the locking mechanism. In the lock mechanism 20B of FIG. 12, a sleeve 26 having a taper 26b with a split 26a and a sleeve 27 having a taper 27a complementary to the taper 26b are fitted into the clamp shaft 11a. If the sleeve 27 is pressed against the sleeve 26 by the piston 28 a of the air cylinder 28 or the like, the position of the clamp shaft 11 a can be fixed by tightening the sleeve 26.

  FIG. 13 shows a second variation of the locking mechanism. The lock mechanism 20C of FIG. 13 has a pair of blocks or plates 29 having a taper 29a that engages with the clamp shaft 11a. The position of the clamp shaft 11a can be fixed by supporting one end of the block or plate 29 rotatably, applying a pressing force to the other end, and sandwiching the clamp shaft 11a with the taper 29a.

  As yet another form, the position of the clamp shaft 11a can be fixed by forming a rack vertically on the outer wall of the clamp shaft 11a, engaging the pinion with the rack, and fixing the pinion.

  FIG. 14 shows the surface pressure measuring mechanism 30. The surface pressure measuring mechanism 30 includes a surface pressure sensor 31, a pressure receiving plate 32, and a circuit board 33.

  The surface pressure measurement mechanism 30 of the present embodiment includes four surface pressure sensors 31A to 31D. Each of the surface pressure sensors 31 </ b> A to 31 </ b> D is installed in a plurality of recesses 10 b formed on the lower surface of the clamp plate 10.

  A control unit (not shown), which will be described later, controls the supply of air S to the clamping force generator 11 based on the output of the surface pressure sensor 31A. Control based on two or more outputs of the surface pressure sensors 31A to 31D is also possible. The surface pressure sensor 31B is a spare sensor, and when the surface pressure sensor 31A fails, the control unit controls the supply of the air S to the clamping force generator 11 based on the output of the surface pressure sensor 31B. .

  The surface pressure sensors 31A and 31B are positions corresponding to the rubber mold mating surface 3c (portions other than the cavity 4 and the gate 4a) in the rubber mold 3 and are located within a range of the outer shape of the rubber mold 3 having the smallest size. It is preferable to arrange. A preferred range R of the installation positions of the surface pressure sensors 31A and 31B is shown in FIG. As shown in the figure, the preferable range R is a range in which the distance from the center C of the clamp plate 10 in the left-right direction is 5 to 17.5 mm, and from the front end E (end portion on the injection nozzle 7 side) of the clamp plate 10. The distance to the rear is in the range of 0 to 20 mm.

  The surface pressure sensor 31A and the surface pressure sensors 31C and / or 31D are used for checking the pressing balance of the clamp plate 10 (appropriateness of the action point of the clamping force F1 in the front-rear direction). When the pressure balance is determined to be inappropriate by comparing the signals of the surface pressure sensor 31A and the surface pressure sensors 31C and / or 31D, the clamp force generator 11 is moved by the clamp force generator moving mechanism 13. The position in the front-rear direction can be adjusted. The clamp force generator moving mechanism 13 is provided with a drive device for driving the clamp force generator 11 in the front-rear direction, and the control unit performs clamping based on the signals from the surface pressure sensor 31A and the surface pressure sensors 31C and / or 31D. The force generator 11 may be configured to automatically move. When the rubber mold 3 is relatively small, the surface pressure sensor 31C can be used, and when the rubber mold 3 is relatively large, the surface pressure sensor 31D can be used.

  FIGS. 16A and 16B show the top and side surfaces of exemplary surface pressure sensors 31A to 31D. In the present embodiment, the surface pressure sensors 31A to 31D are carbon resistance type sensors. The surface pressure sensors 31A to 31D include a substrate 31a on which a circuit pattern (not shown) including a pair of comb electrodes is formed, and terminals 31b and 31b electrically connected to the comb electrodes. A carbon film 31d is attached to the upper part of the comb-shaped electrode via a spacer 31c, and the change in pressure is detected by changing the conductive resistance between the comb-shaped electrodes according to the pressure acting on the carbon film 31d. It is a mechanism. The carbon resistance type sensor has advantages such as very thin, small shape and high durability, although the surface pressure detection accuracy is not so high.

  The surface pressure sensors 31 </ b> A to 31 </ b> D are installed in the recesses 10 b formed in the clamp plate 10 so that the surface of the carbon film 31 d substantially matches the lower surface of the clamp plate 10. The terminals 31b and 31b of the surface pressure sensors 31A to 31D are soldered to the wiring on the circuit board 33 through the wiring holes 10c provided in the clamp plate 10 so as to avoid the movable part of the floating mechanism 12.

  A pressure receiving plate 32 is preferably attached to the lower surface of the clamp plate 10. The pressure receiving plate 32 is preferably made of a material having a lower hardness than the rubber mold 3 (for example, rubber, plastic, etc.). The pressure receiving plate 32 may be attached to the lower surface of the clamp plate 10 so as to cover the entire lower surface of the clamp plate 10. Since the clamp device 5C of the present embodiment includes the lock mechanism 20A, it is preferable to make the pressure receiving plate 32 as thin as possible. This is because the lock mechanism 20 </ b> A clamps the rubber mold 3 via the pressure receiving plate 32, which may reduce the lock effect. Since the thickness of the surface pressure sensors 31A to 31D of this embodiment is extremely thin and about 0.05 mm (the operation range of the carbon film 31d is less than that), the thickness of the pressure receiving plate 32 may be thin. Although depending on the hardness of the pressure receiving plate 32, the thickness of the pressure receiving plate 32 is preferably 0.03 to 5 mm, more preferably 0.05 to 3 mm, and particularly preferably 0.1 mm to 2 mm. It is. In the case of a clamping device that does not use the lock mechanism 20A, the thickness of the pressure receiving plate 32 is not limited, and the pressure receiving plate 32 having a large thickness may be used.

  FIG. 17 shows a mechanism of surface pressure measurement by the surface pressure measurement mechanism 30. As shown in FIG. 17 (a), when there is no pressure receiving plate 32, unless the rubber mold 3 is deformed, the clamping force does not act on the carbon film 31d, so the pressure of the rubber mold 3 may not be detected properly. Conceivable. When the pressure receiving plate 32 having low hardness is arranged on the lower surface of the clamp plate 10, as shown in FIG. 17B, the pressure receiving plate 32 is deformed so that the clamping force easily acts on the carbon film 31d. The pressure can be detected more reliably.

  The circuit board 33 carries a circuit pattern for collecting the wirings of the surface pressure sensors 31A to 31D and connecting them to the control unit. In order to ensure insulation between the circuit pattern and the clamp plate 10, the circuit board 33 is attached to the clamp plate 10 via a spacer 33a. The circuit board 33 has a U shape so as to avoid the movable part of the floating mechanism 12.

  The clamp device 5C may include a target value input unit and a control unit similar to the target value input unit 40 and the control unit 50 of the clamp devices 5A and 5B. In the present embodiment, the control unit controls the clamping force F1 by controlling the supply of the air S to the clamping force generator 11 based on the output of the surface pressure sensor 31A. In actual work sites, it is not uncommon for wax molds to be produced several hundred to thousand times a day using the clamp device 5C. When the surface pressure sensor 31A or its wiring breaks down due to repeated use, etc., the control unit can control the supply pressure of the air S to the clamping force generator 11 based on the output of the surface pressure sensor 31B. .

  The preferred embodiments have been described above, but the above embodiments are examples, and the present invention can be modified in various ways within the scope of the claims.

  For example, in the embodiment of the clamp device 5C, an example in which the carbon resistance type surface pressure sensors 31A to 31D are used has been described, but other types of sensors can also be used. For example, a conductive rubber resistance type sensor using a rubber plate made of conductive fine powder such as metal may be used. However, the conductive rubber resistance type sensor is thicker, less durable, and less accurate than the carbon resistance type sensor. A high precision surface pressure sensor can be constructed by applying a strain gauge or magnetic sensor, but it is thin and difficult to reduce in shape. Among the currently available surface pressure sensors, the carbon resistance type is most suitable.

  Although the case where the surface pressure sensors 31 </ b> A to 31 </ b> D are installed on the lower surface of the clamp plate 10 has been described in the above embodiment, the surface pressure sensors 31 </ b> A to 31 </ b> D may be installed on the upper surface of the mounting table 9.

  In the above embodiment, the surface pressure sensor 31B is a spare sensor, and the surface pressure sensors 31C and / or 31D have been shown to be used for checking a pressing balance, but the two surface pressure sensors 31A to 31D. The supply pressure of the air S may be controlled using the average value of the above outputs.

  In the above embodiment, the case where the number of the clamping force generators 11 is one is shown. However, a plurality of small (small output) clamping force generators 11 are arranged in the front-rear direction, and the surface pressure sensor 31A and the surface pressure sensor 31A are arranged. A modification in which the clamp force F1 (supply pressure of the air S) of each clamp force generator 11 is controlled using the signal of the pressure sensor 31C or 31D so that the pressing balance in the front-rear direction is uniform is also possible. In this variation, the clamping force generator moving mechanism 13 can be omitted. The positional relationship and the number of the surface pressure sensors 31A, 31C, 31D in the front-rear direction are not limited to those in the above embodiment, and can be adjusted as appropriate. In this modification, the pressure balance in the front-rear direction is not made uniform, but the pressure balance in the front-rear direction is adjusted according to the characteristics of the rubber mold 3 and the arrangement and shape of the cavity 4 (front of the rubber mold 3). It is also possible to make the clamping force of the part stronger or weaker than the rear part. Thereby, better wax injection may be possible.

  The clamping device of the present invention can have the following effects in addition to the effects described above.

  As described above, the clamp force generator 11 is preferably an air cylinder that moves the clamp shaft 11a up and down by the supply of air S and the action of the return spring 11b. The thickness of the rubber mold 3 varies, and the thickness of the rubber mold positioning insertion plate 9a (acrylic plate) varies depending on the customer. If the thickness of the rubber mold 3 or the thickness of the rubber mold positioning / inserting plate 9a changes, the amount of deflection of the return spring 11b when the rubber mold 3 is clamped is different. A difference occurs in the force F1. That is, even if the pressure of the air S applied to the clamp force generator 11 is constant, the clamp force F1 is different if the thickness of the rubber mold 3 or the thickness of the acrylic plate (rubber mold positioning insertion plate 9a) is different. This makes it more difficult to obtain an appropriate value for the clamping force, which is one of the reasons why the clamping force must be changed in various ways. Since the present invention controls the clamping force based on the actually measured surface pressure Pm, the clamping force can be made constant regardless of the difference in the thickness of the rubber mold 3 or the difference in the thickness of the acrylic plate. obtain.

  INDUSTRIAL APPLICABILITY The present invention can be applied to the manufacture of a clamping device and a wax mold used for fixing a rubber mold in wax mold injection molding for manufacturing small articles such as jewelry and accessories, and industrial products.

DESCRIPTION OF SYMBOLS 1 ... Prototype 2 ... Parts 3, 3 '... Rubber mold 4, 4', 4 '' ... Cavity 5, 5A, 5B ... Clamping device 5a ... Clamp mechanism part 5b ..Up-and-down moving mechanism 5c ... Previous moving mechanism 6 ... Wax type injection molding machine 7 ... Injection nozzle 8 ... Clamp mechanism unit housing 9 ... Rubber type mounting table 10 ... Clamp plate DESCRIPTION OF SYMBOLS 11 ... Clamping force generator 11a ... Clamp shaft 12 ... Floating mechanism 13 ... Clamping force generator moving mechanism 14 ... Left-right moving mechanism 20, 20A-20C ... Locking mechanism 21 ... · Lock rod 21c ··· Engagement portion 24 ··· Air cylinder 24b · · · Drive shaft 25 · · · Wedge receiving members 25d and 25e · Friction portions 30 and 30A to 30D · · · Surface pressure measuring mechanism 31 ... Surface pressure sensor 31a ... Substrate 31b ... Terminal 31d ... Carbon film 31c ... Spacer 32 ... Pressure receiving plate 33 ... Circuit board 33a ... Spacer 40 ... Target value input means 50 ... Control unit

Claims (7)

A mounting table for mounting the rubber mold;
A clamp plate movable in the vertical direction;
A clamping force generator for applying a clamping force to the clamping plate;
A clamping device for wax mold injection molding that clamps the rubber mold between the mounting table and the clamp plate,
A surface pressure measuring mechanism for measuring the surface pressure generated in the rubber mold;
An input means for inputting the surface pressure target value;
The clamp apparatus further comprising a control means for controlling the clamping force based on the surface pressure target value and the surface pressure measured by the surface pressure measuring mechanism. The clamp apparatus according to claim 1, further comprising a lock mechanism that fixes a vertical position of the clamp plate with respect to the mounting table. The clamping device according to claim 1 or 2, wherein a pressure receiving plate having a hardness lower than that of the rubber mold is attached to a lower surface of the clamp plate. The surface pressure measuring mechanism has a surface pressure sensor,
The said surface pressure sensor is attached to the recessed part formed in the lower surface of the said clamp plate, The clamp apparatus as described in any one of Claims 1-3 characterized by the above-mentioned. The injection of the wax into the rubber mold is performed in a state where the clamp device is adjacent to the wax mold injection molding machine,
The wax injection direction is a first direction, and a direction in a horizontal plane perpendicular to the first direction is a second direction.
In the surface pressure sensor, the distance in the first direction from the end of the clamp plate on the wax-type injection molding machine side is 0 to 20 mm, and the surface pressure sensor from the point of application of the clamping force on the clamp plate The clamping device according to claim 4, wherein the clamping device is installed in a region in which the distance in the second direction is 5 mm to 17.5 mm. The clamp device according to claim 4 or 5, wherein a plurality of the surface pressure sensors are installed at spaced positions in the first direction and / or the second direction. A method for producing a wax mold using the clamping device according to any one of claims 1 to 6,
A first step of clamping the rubber mold according to the control of the control means;
A second step of maintaining the clamping force at the end of the first step;
A method of manufacturing a wax mold, comprising: a third step of injecting wax into the rubber mold after a predetermined time has elapsed since the end of the first step.

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